1. Field of the Invention
The present invention relates to a forging press apparatus for press forging a raw material, a controller of an automation device used therefor, and a shut height controller. More particularly, the present invention relates to a device for preventing the reduction of productivity caused by out of coincidence of the synchronism between the production tempo of a heating furnace and that of an automation device for supplying a raw material to a forging press in a forging press line, and to a device for adjusting a shut height.
2. Description of the Related Art
A load controller for enhancing the accuracy of a product thickness is conventional proposed in an automatic mechanical forging press apparatus (refer to Registered Utility Model No. 2534472 and Japanese Unexamined Patent Publication (JP-A) No. 7-47500, hereinafter, referred to as Conventional Arts 1 and 2).
The shut height controller according to Conventional Art 1 is included in a forging press apparatus for forging raw materials to forged products by continuously striking them in die components.
The shut height controller includes a measuring unit for obtaining a measured striking load by continuously measuring a striking load in the state that a raw material is located in die components. The measuring unit has load sensors disposed on the support columns of a cabinet and a load converter for calculating a die-kiss load from the output from the load sensor and outputting it.
Further, the shut height controller has an adjustment unit. The adjustment unit compares a reference striking load predetermined by a CPU with the measured striking load from the load converter and determines the deviation therebetween. When the deviation exceeds a predetermined allowable value, the adjustment unit outputs a hydraulic motor drive command to a hydraulic motor based on a shut height correction value corresponding to the deviation and adjusts a shut height.
Further, the crank press apparatus disclosed in Conventional Art 2 includes a lower die component disposed on a bed and an upper die component mounted on a slide and moves the slide upward and downward by a crank mechanism. The crank press apparatus includes abutment surfaces disposed in the vicinity of both the upper and lower die components in addition thereto. The abutment surfaces are abutted against each other before the upper and lower die components are completely closed when the slide is moved downward. In addition, the abutment surfaces are arranged such that the striking load of a press is set larger than a load necessary to forging and the striking load of the press is controlled by causing the abutment surfaces to be abutted against each other in a forging operation to thereby secure the accuracy of the thickness of a product.
At present, however, the measures for the enhancement of accuracy of the thickness of a product in the forging press apparatuses employed in Conventional Arts 1 and 2 can only cope with the frequent change of striking conditions, which are required by the recent increase of operating speed of equipment, as the premise of the enhancement of the accuracy at the best and cannot cope with the enhancement of the accuracy of thickness of the product which is intrinsically required.
As a specific example, when certain predetermined conditions are set in a press, that is, when, for example, such conditions that raw materials to be forged are supplied to all the processes in the press and all of them are to be struck, all the raw materials are always struck conventionally. However, there may be a case in which some of the raw materials to be forged temporarily lack in some processes due to the difference between the production tempo of a heating furnace and that of a forging press main body. In particular, when the speed of equipment is more increased, this phenomenon frequently occurs.
In such a case, the thickness of a product cannot be controlled by the feed-back of a load and a total load is dispersed, whereby the accuracy of the thickness of forged products is deteriorated. As a result, when some raw materials to be forged lack, the accuracy of a product thickness cannot be enhanced in total.
As described above, it is conventionally difficult to perfectly synchronize the cycle time of a heating furnace with that of the automation device (for example, a transfer feeder) of a forging press in a forging press line. The reasons are as described below.
In general, a heating furnace adjusts the production tempo of by the feed speed of a billet. The billet feed mechanism of the heating furnace is generally arranged such that the billet is clamped between upper and lower gears and the gears are rotated. Thus, the feed speed of the billet is determined by controlling the number of revolution of the gears. Therefore, when the billet slips between the gears, when an end surface of the billet is obliquely cut or the billet has burrs formed thereon, intervals exist sometimes and do not exist sometimes between billets, whereby actual production tempos are varied. Because of the above reason, it is difficult to establish perfect synchronization between the heating furnace and the forging press.
When the heating furnace is not in synchronization with the forging press, the following problems arise.
(i) When the production tempo of the heating furnace is faster than that of the transfer feeder, the number of billets supplied from the heating furnace is larger than the throughput of the forging press. As a result, an abnormal state is caused in the transfer of billets between the heating furnace and the forging press or a rate of operation is lowered or rejected products (defective products) are increased because billets are rejected, whereby productivity is lowered.
(ii) When the production tempo of the heating furnace is slower than that of the forging press, the number of billets supplied from the heating furnace is smaller than the throughput of the forging press. Thus, billets lack in some of the multi-process die components in the forging press. Therefore, since a total forging load is varied, the accuracy of thickness of forged products is deteriorated and accordingly products of defective accuracy are made and productivity is lowered thereby.
However, since the adjustment method shown in the above item (i) permits the generation of rejected products from the beginning of the execution of the method, the adjustment by which productively is lowered is not practically usable and is not employed.
Therefore, in many cases, adjustment is carried out such that the production tempo of the heating furnace is made somewhat slower than that of the transfer feeder as shown in the item (ii). Thus, there is caused a phenomenon that raw materials partly lack in a synchronized state.
The phenomenon of the partly lack of raw materials will be described below in detail. It is supposed that all the raw materials are struck in the four processes of a forging press at the production tempo in which a cycle time is set to 3 seconds (productivity; 1200 pieces/hour). All the raw materials striking is one of transfer methods in the production performed by press by which raw materials to be forged, which are located in all the processes (from first to fourth processes) in multi-process die components, are forged at a time by one press stroke and transported.
In the above case, while the transfer feeder of the forging press operates at a cycle of 3 seconds, billets are supplied from the heating furnace at a little longer cycle time because of the above reason.
When the slight deviation between the cycle times is accumulated to 1 cycle time, the phenomenon of the partly lack of raw materials is caused. Specifically, the raw materials, which were forged and produced in all the first to fourth process of the forging press, are forged in only the second to fourth processes excluding the first process. When the lack of raw material in the first process occurs once, forging is carried out only in the first, third and fourth processes excluding the second process in the next cycle. Then, the lack of raw material sequentially occurs in the third process and the fourth process.
It is supposed that the deformation of a press is 2 mm and the thickness of a product is 25 mm with a forging load of 2000 tf (tons) when forging is carried out in all the processes. When the partial lack of raw material occurs in the above state, the load of the forging process in which the partial lack of raw material occurs is subtracted, for example, when there is a forging load of 1000 tf in the third finish process, a load as large as 1000 tf is lost so that the deformation of the press is made to 1 mm which is half the original deformation and the thickness of the product is made to 24 mm.
A "load controller for automatic mechanical forging press" is proposed in Japanese Examined Patent Publication (JP-B) No. 6-77878 (referred to as Conventional Art 3) as a slide adjustment mechanism for solving the above problem.
The automatic mechanical forging press shown in Conventional Art 3 comprises a forging press section, which is composed of a plurality of upper die components mounted in a row on the lower bottom of a slide suspended from an eccentric shaft through a connecting rod so that it can be freely moved up and down and lower die components disposed in parallel with each other on the upper surface of a bed confronting the upper die components and a transfer section for supplying raw materials to be forged and sequentially transferring them to each process and taking out forged products.
The automatic mechanical forging press includes a forged product detection unit for detecting whether or not raw materials or forged semi-products exist in the respective die components, an arithmetic operation and control unit for issuing a prestored additional supply execution command in response to the detection signal from the forged product detection unit, and an actuating unit for rotating an adjust lever which is eccentrically fitted on a lift pin inserted into a connecting rod at the lower portion thereof by a desired angle by hydraulic force in response to the execution command so as to move the position of a lower dead point.
However, there is a limit in the adjustment of the slide at a high speed also in Conventional Art 3, and further there is also a problem in that frequent actuation of the slide is not good from the view point of durability. Thus, Conventional Art 3 is not used as a countermeasure for the partial lack of raw materials.